Turboventilator for the input of oxygen into liquids

ABSTRACT

A turbo ventilator for mechanically aerating sewage to activate the sludge during the biological purification is disclosed. A vertical shaft mounts a plurality of circumferentially spaced box-like jet formers which are rotated at the surface of the liquid. These jet formers supply upstanding radially spaced vanes extending between upper and lower enclosure plates to provide short, box-like jet forming tubes. As these jet formers are rotated in the surface layer of the tank, water is taken in a substantially horizontal plane and is accelerated to produce horizontally travelling jets that entrain bubbles of air. These jets are discrete enough and have enough momentum to reach the walls of the tank whereupon they are deflected downwardly to further oxygenate the body of water in the tank. The water is returned to the inlet sides of the jet former tubes from a whirlpool at the center of the tank and makes smooth and nonturbulent transition to a horizontal flow pattern before it re-enters the aerator jet formers.

tinned States Patent Kalbskopi [54] TURBOVENTILATOR FOR THE INPUT OFOXYGEN INTO LIQUIDS [72] Inventor: Karl-Heinz Kalbskopf, Oberhausen,

Germany [7 3] Assignee: FMC Corporation, San Jose, Calif.

[22] Filed: May 3, 1971 [21] Appl. No.: 139,475

Related us. Application Data [63] Continuation-impart of Ser. No.71,046, Sept.

10, 1970, abandoned.

[52] US. Cl. ..261/91, 261/120, 210/219, 210/220, 210/242 [51] Int. Cl...BOlf 3/04 [58] Field of Search ..261/91, 120; 210/219, 220, 210/242 [56] References Cited UNITED STATES PATENTS 3,573,203 3/1971 Kaelin..261/91 3,360,460 12/1967 Weston ..261/91 3,329,407 7/1967 Clough eta1. ..261/91 3,576,316 4/1971 Kaelin ..261/91 3,591,149 7/1971 Auler..210/219 3,423,077 l/ 1969 Gloppen ..261/91 [451 Nov. 28, 19723,341,450 9/1967 Ciabattari et a1. ...261/91 3,539,158 11/1970 Roos..261/91 mm Examiner-Tun R. Miles 1 Assistant Examiner-Steven H.Markowitz Attorney-F. W. Anderson and C. E. Tripp ABSTRACT A turboventilator for mechanically aerating sewage to activate the sludgeduring the biological purification is disclosed. A vertical shaft mountsa plurality of circumferentially spaced box-like jet formers which arerotated at the surface of the liquid. These jet formers supplyupstanding radially spaced vanes extending between upper and lowerenclosure plates to provide short, box-like jet forming tubes. As thesejet formers are rotated in the surface layer of the tank, water is takenin a substantially horizontal plane and is accelerated to producehorizontally travelling jets that entrain bubbles of air. These jets arediscrete enough and have enough momentum to reach the walls of the tankwhereupon they are deflected downwardly to further oxygenate the body ofwater in the tank. The water is returned to the inlet sides of the jetformer tubes from a whirlpool at the center of the tank and makes smoothand nonturbulent transition to a horizontal flowpattern before itre-enters the aerator jet formers.

20 Claims, 1.8 Drawing Figures PATENTEDNHVZB 912 3.704.009 SHEET 1 BF 6,

IN VENTQR. KARL-HEINZ KALBSKOPF BYjga ATTORNEYS PATENTEDnuvzs I972 SHEET3 OF 6 PATENTED NOV 2 8 I872 SHEET 5 OF 6 FIE IZ PATENTEDuavza I372 3.704.009

sum 6 or 5 22 FIB 1 1 TURBOVENTILATOR FOR TIE INPUT OF OXYGEN INTOLHQUHDS REFERENCE TO RELATED APPLICATIONS DESCRIPTION OF PRIOR ARTVarious systems of mechanical surface ventilators are known for theventilation of water and waste water and for the supply of oxygen toactivated sludge during biological waste-water purification. The mainfunction of such mechanical surface aerators is provision of an oxygeninput to the water that is obtained by mechanical action on the surfaceof the water that entrains and mixes air bubbles with the water.However, at the same time, mechanical surface aerators produce somecirculation, by means of which the aerated water is mixed with dissolvedand solid substance particles in the tank, preventing the sedimentationof substances that would otherwise be deposited.

A frequently utilized type of prior mechanical surface aerator is aturboblower, and various types of construction of such rotary aeratorsare known. The effects of oxygen input and of water circulation with theprior constructions mentioned, are obtained either by the rotarymovement of stirring blades secured to the turbine, or by means of aspraying and blast action of the water conveyed through the blades orducts of the turbine.

In the interests of economy, efforts have been made in prior turbineaerators to obtain a high oxygen input and high circulation volume whilerequiring a small consumption of energy. However, recent priordevelopments of turboventilators frequently correspond to conventionaltypes of construction employed as hydraulical impellers for centrifugalpumps, but having lower speeds of rotation.

The U.S. patent of Thikotter U.S. Pat. No. 3,479,017, Nov. 18, 1969,shows a common type of radial blade rotor, the blades being covered by atop plate.

The U.S. patent to Weston U.S. Pat. No. 3,360,460, Dec. 26, 1967 shows arotary plate having peripheral depending vanes radially disposed andcircumferentially spaced. This construction is subject to the samedeficiencies as Thikotter, previously mentioned.

In U.S. patent to Kalinske et al U.S. Pat. No. 3,154,601, Oct. 27, 1964,the top plate is submerged below the surface of the water by a criticaldistance. Substantial direction changing forces are exerted against thewater and this device is principally a mere turbulence producingapparatus.

The U.S. patent to Auler et al U.S. Pat. No. 3,473,790, Oct. 21, 1969shows a rotor that rotates within a fixed baffle at the surface of thewater. Bubbles are created in sheets of water, some of which leave thesurface of the water and flow over the top of the baffle,

' while others flow under the bafile.

SUMMARY OF THE INVENTION Because of its rotating motion, during theoperation of a turboventilator there is formed below theturboventilator, a vertical water whirlpool, that returns the water tostirring blades, paddles or ducts of the turbovenu'lator. For efiectiveoxygenation of the body of liquid, the water direction must be changedby and directed radially. Even when the whirling movement of the waterbelow prior turboventilators is braked by deflector crosses or deflectorplates, there are created during the intake and deflection of the water,considerable turbulence losses, that on the conventionalturboventilators have an unfavorable effect on water circulation.

In addition to the provision of effective air-mixing effects atthe-aerator turbine, a high water circulation performance across thetank is a condition for an economical utilization of the oxygen input atthe aerator. However, conventional turboventilators, where an effort ismade to obtain these conditions by hydraulically favorable types onconstruction, are of a very complicated and expensive construction.

In contrast to the prior and conventional turboventilators possessingvortex producing plates, feeder blades or ducts, in the presentinvention the water is formed into long lasting aeration jet streams bymeans of jet producing devices, and without turbulent deflection at theaerator as the water is'taken from below the turbine and hence out ofthe whirlpool created there.

The aerator of the present invention comprises a plurality ofcircumferential spaced jet forming arms, each arm having box-like jetformers which are mounted to rotate at the surface layer of the liquid.These jet formers are bounded by upstanding, radially spaced vanes. Thevanes are generally parallel and extend between upper and lower closureplates. The jet forming arms (made up of these box-like jet formers) arecircumferentially spaced, thereby providing for unobstructed entry ofliquid from between and in front of the arms and for entry of air fromabove the aerator. The vanes are short circumferentially and are widelyspaced radially, thereby forming box-like structures. The vanes areinclined from a tangent to their path of motion in a direction such thattheir leading edges have a smaller radius of rotation than theirtrailing edges. As a result of this construction, the jet formers of thepresent invention accelerate the surface layer of liquid into diverging,horizontal jet streams that embody entrained air bubbles. These jetstreams travel onto the walls of the tank (where used), whereupon theyare diverted downwardly and hence carry air entrained at the aera-' tordown into the main body of liquid into the tank for efficient aerationthereof.

it is a feature of the present invention that the water need notabruptly-change its direction from a vertical to a horizontal motion atthe entrance to aerator jet formers and hence clogging and depositingout of solid materials does not interfere with the aerating action.

The rotation of the box-like jet former structures of the presentinvention, at a velocity sufficient to produce a given degree ofaeration, requires less horsepower than that required by prior aeratorsof the type previously mentioned, for a given oxygen input to theliquid.

BRIEF DESCRIPTION OF THE DRAWINGS .FIG. 1 is a side view of aturboventilator or aerator constructed in accordance with the presentinvention.

FIG. 2 is a plan view of the apparatus of FIG. 1.

FIG. 3 is a view, on a reduced scale, showing the turboventilator in atank of water.

FIG. 4 is a side view of a modified form of turboventilator.

FIG. 4A is a section thru a fabricated tube jet former.

FIG. 5 is a plan view of a modified form of an aerator having six jetforming arms.

FIG. 6 is a side elevation of the aerator of FIG. 5 with the hub brokenaway.

FIG. 7 is an enlarged section of the hub.

FIG. 8 is an enlarged plan view of a jet former arm with parts brokenaway.

- FIG. 9 is a front elevation of the arm of FIG. 8.

FIG. 10 is an end view of the arm.

' FIG. 11 is a still further enlarged plan view showing the geometry ofan aerator vane.

FIG. 12 is a plan view of an aerator like that of FIG. 5 but havingeight arms instead of six as in FIG. 5.

FIG. I3 is a plan view of still another form of aerator mounting l0 jetforming arms.

FIG. 14 is a section of still another form of aerator wherein the jetforming arms are inclined upwardly from the horizontal. v

FIG. 15 is a view like FIG. I0 showing a modified jet former havinginclined cover plates.

FIG. 16 is an enlarged plan operational diagram showing the jet formingaction.

FIG. 17 is a diagram showing the aerator in a small tank thatillustrates the formation of divergent jet streams by the aerator.

DETAILED DESCRIPTION As illustrated in an exemplified embodiment inFIGS. 1 3 the jet producing devices or jet former units, indicatedgenerally at l, comprise two superposed plates 2 and 2a and severalvertical jet deflecting plates or vanes 3, thereby providing a number offlow or jet forming chambers 4. These chambers have water inlets 4a attheir leading ends and jet stream outlets 4b at their trailing ends(FIG. 2).

The individual jet producing chambers ,4 can also be assembled fromprefabricated rectangular or tube profiles, as indicated at 16a, 16b and16c, FIG. 4A.

Two, three or more of these jet producing units, as shown in FIG. 1 aresuspended from radial arms 5, by posts 5a to produce a straight throughturbine. The jet formers 1 are mounted with a slight tilt in relation tothe horizontal, in the form shown in FIG. I.

As seen in FIG. 3, during rotation of the aerator at the surface layerof water in a tank T, water is supplied to the aerator from thewhirlpool W below. However, because of the unobstructed space betweenthe jet forming arms, as the water actually enters the leading or intakeapertures 4a of the individual chambers 4 of the jet aerators, relativemotion between the jet formers and the water is substantially in ahorizontal plane.

The vertical deflector plates or vanes 3 of the jet producing devicesare inclined from a tangent to their path of motion and in a directionthat can be defined as toward the direction of rotation of the turbine.Stated differently, the inclination is such that 'the leading edges ofthe vanes have a smaller radius of rotation than their trailing edges(FIG. 2). Thus during the flow of the water through the jet producingdevices there are created zones of low pressure, where air is suckedinto the jet flow.

The water is accelerated by the vanes 3 and then is flatly projectedthrough the outlet apertures 4b. This produces a plurality of divergingjet streams S that embody entrained air bubbles A. These streams reachthe tank walls (FIG. 3) and are diverted down, carrying the entrainedair into the body of tank liquid. The liquid returns to the aerator viathe whirlpool W, as explained. The change in direction of the water fromthe whirlpool W to the inlet apertures 4a is relatively gradual andsmooth and is accomplished without the use of deflecting plates orbaffles. Thus there is little turbulence at the inlets 4a of the jetformer chambers 4 and hence any entrained material such aspaper, etc.does not settle out and clog the aerator. Also, the long lasting,horizontal jet streams S and their entrained air bubbles A are producedwith smaller power requirements than those of prior aeration thatprovide the same oxygen input.

The quantity of water projected in the form of the jets S is basicallydetermined by the size of the cross section apertures of the jet formersthrough which the water flows, and by the speed of rotation of theaerator. Typical dimensions for these parts will be described in detailrelative to the modifications of FIGS. 5 13.

By changing the depth of immersion as well as by changing the speed ofthe aerator, it is possible to regulate the quantity of water that isprojected by the jet streams, and thus also the amount-of entrained airand hence the input of oxygen that is created by the jet effect.However, in all cases the aerator acts in the surface layer of water inthe tank;

The present aerator also provides constructional advantages in that thejet producing devices can be readily made up witha selected number ofchambers 4, and the dimensions of the chambers are readily determined bysimple fabrication techniques. The jet formers are simple to fabricateand the desired number of individual jet forming chambers 4 can bereadily provided on the distributor arms 5 of the aerator. Anotheradvantage lies in the fact that individual jet former units 31 can besecured by means of a joint (not shown) in such a manner that they canhave selected inclinations with the water surface, in which manner it isfurther possible to vary the output of the aerator.

The embodiment of FIG. 4 represents a further development of aturboventilator shown in FIGS. 1, 2

and 3 which reduces the weight load on the drive mechanism via the driveshaft, and improves the flow deflectors 13 extend between the plates 12,12a as in the previous embodiment, to provide parallel jet formingchambers 14 of rectangular construction. The cylindrical float F and thecone are watertight and may be formed of plastic or metal. The float maybe either round or polygonal, and the arms 11 connected laterally to thefloat F by screws (not shown).

Because of the buoying forces of the composite float F and cone 15 towhich the jet producing arms 11 are directly secured, the weight load onthe drive system (not shown) and on the drive shaft 16 is reduced. Bymeans of the preferably cone-shaped construction of the lower portion 15of the float, the desired centering of the flow immediately below theaerator is obtained, and this improves the outflow conditions in theindividual jet producing chambers 14.

An additional advantage in the construction of FIG. 4 is the eliminationof the mounting arms 5 and posts 5a shown in FIGS. 1 and 2. Since icecan form under certain conditions on these mounting members duringwinter, this leads to an additional load on the drive aggregate.

As mentioned, the jet producing arms 11 can be detachably secured to thefloat F in a manner that is known as such, for instance by screws. Thesize of the float is suitably adapted to the length and number of thejet producing units secured to it, as well as to the buoying forcesdesired, and hence there are many possible combinations.

The aerator shown in FIGS. 5 through 12 embody a preferred embodiment ofjet formers and otherwise resembles the float type aerator previouslydescribed in connection with FIG. 4. The construction of FIGS. 5, l2 and13 represent designs wherein the floats are modified to receive 6, 8 and10 jet forming arms of the type previously described. However, certainimprovements in the jet forming arms are also disclosed in theembodiments now to be described in detail.

The aerator (referring to FIGS. 5 7), has a central float indicatedgenerally at 21 that mounts six jet forming arms 22 (FIG. 5). As seen inFIGS. 6 and 7, the float 21 is of closed cylindrical construction andhas upper and lower circular plates 23, 24 that are welded to a centraltube 26. The upper end of the tube .26 is flanged at 28 and is bolted toa similar flange mounted on a depending drive shaft 30. The drive shaft30 is rotated by a motor or other source of power in a conventionalmanner.

A cylindrical wall 32 is welded adjacent the periphery of the upper andlower plates 23,24 to leave projecting mounting flanges for jet formingarms 22. Radial reinforcing plates 33 extend between the central tube 26and the wall 32. A water tight cone 34 is welded to the lower plate 24to form a centering cone and float construction in the manner previouslydescribed.

In the embodiment shown, the jet forming arms 22 have upper and lowercover plates 36,38 between which extend generally vertical vanes ordeflectors 40 having the general purpose of those described in theprevious embodiments. The cover plates 36,38 and the vanes 40 provideindividual, box-like jet forming chambers 42, although, as previouslymentioned, this number may be varied. The jet forming arms 22 aresecured to the peripheral flanges on the upper and lower float plates23,24 by upper screw bolts 39 and lower screws or bolts 39a.

Additional details of the jet forming arms 22 appear in FIGS. 8 11. Forexample, the ends 36a,38a of the upper and lower plates 36,38 areinclined to the direction of the path of the arms so that the leadingedges of each plate are shorter than their trailing edges. In theexample being described, the angle of inclination of the ends of theplates 36,38 to the path of the plates is about 15.

The jet former arms 22 extend a distance a up to the first vane 40 (FIG.8) and the vanes are provided along the remaining length b. The vanes 40are uniformly spaced by a distance 0, and have a circumferential extentindicated at d. As seen in FIG. 7, the float 21 has a major diameterindicated at n and the diameter of the central tube 26 is indicated atp.

As seen in FIGS. 8 and 10 the lower cover plate 38 is circumferentiallycoextensive with the deflector vanes 40 and hence has a width equal tod. However, the upper plate 36 has a greater width e and hence overhangsthe trailing edges of the vanes 40 by a distance indicated at f in FIGS.8 and 10. The plate 36 overhangs the leading edges of the vanes 40 by asmaller distance, indicated at f Thus the narrow, lower cover plate 38does not impede access to the leading ends 424 of the jet formingchambers 42. The upper plate 36, although it is wider than the vanes, isnormally above the surface of the water (FIG. 10) and hence does not actas a direction changing baffle for water entering the chambers 42.

By way of presenting design examples for a given sized installation sothat those skilled in the art may practice the invention, the dimensionsof the preferred vane constructions along with other dimensionsillustrated in FIGS. 8- 11 are given in Table l, to follow.

Another improvement of the preferred construction now being describedover that of the previous embodiments, relates to the shape of the vanes40. In the preferred embodiment these vanes are curved in the mannerbest seen in FIG. 11. Preferably the curvature of the vanes is compound,in that the vanes are made up of a circular arc portion 40a and astraight portion 40b. The straight portion 40b is leading, and isinclined at an angle g of about 15 with respect to a tangent to themotion of the vanes through the water.

Since the vanes are generally inclined from a tangent to their path ofmotion through the water, the blades accelerate the water in thehorizontal plane thereby increasing .its velocity and facilitating thecreation of jet streams in the manner previously described. The durvedconstruction of the individual vanes coupled, with their parallelorientation in the jet forming arms, further contributes to theacceleration of the water as it passes through the chambers 42 and henceto formation of the jet streams S. In addition to the action of thevanes due to their inclination and due to the curvature of the vanesindividually, consideration will show that the effective width of thepassageway 42 formed between vanes 40 progressively decreases slightly.Thus acceleration of the water into jet streams results from both theinclination of the vanes when from a tangent to their path of motion andfrom their curved construction coupled and their parallel disposition.This construction accelerates the water into the jet streams S withoutcreating turbulence and at horsepower requirements lower than those ofprior aerating devices.

The construction of the aerator 20a, FIG. 12 embodies the same jetforming arms 22 employed in the aerator 20 of FIGS. 5 7. However, theaerator 20A is formed with eight jet forming arms 22 (also at equalangular spacings), instead of six arms as in FIG. 5. In the form of FIG.12, a float 21a is employed which is like the float 21 previouslydescribed in connection with FIG. 5 but has a larger diameter n toaccommodate the eight arms 22 instead of six as before, but at about thesame substantially circumferential spacing. The cone 34 (seen only indotted lines in FIG. 12) is of the same construction and size as cone 34employed in the construction of FIGS. 5 7. The aerator 20A of FIG 12 isrotated to give about the same tip speed to the jet forming arms as thatimparted to the arms of FIG. 5. However, since there are more arms inthe FIG. 12 construction, there will be a greater oxygen input with anattendant increase in horsepower requirements due to the increasedaeration.

FIG. 13 shows an aerator 20B mounting ten jet forming arms 22. The onlydifference between this construction and those previously described isthat here the float 21b has a diameter n that is still larger than thatof those previously described. However, the cone 34 has substantiallythe same dimensions as the cones provided with the previous embodiments.

As previously mentioned, various preferred design details and operatingcharacteristics of the aerator just described are given in Table I,below.

Table I Design Details Jet Arm Dimensions in Inches Preferred Geometry(FIGS. 8-! l) Spacing u |3.or l8.5 Arm b 34.5 d=0.5c to l.Oc Bladespacing c 7.86 j= LOc to l.5c Blade length d 7.86 angle g 10 to 30,l5

preferred. Plate width e [4.2 Plate overhang f 4.0 Tip Speed ofInnermost Vane Vane height j 13.25 10 20 feet/sec. Straight portion k3.3 Arm Angle 5 (FIG. 14) Curved portion 1 6.2 l 30 Radius m 6.9

Hub Dimensions in Inches (FIG. 7)

l0 arms 8 arms 6 arms (FIG. 13) (FIGv 12} (FIG. Hub diameter 11 8 L2557.5 34.2 Tube diameterp 13.0 10.4 8.75

Cone All Forms (FIG. 6)

Cone height q 23.5 inches Angle r 68 The aerator 20C of F IG. 14 is likethe construction of FIGS. 5, l2 and 13 except in this case, the jetforming arms 22c are mounted on an inclination angle s relative to thehorizontal of the float 210. The inclination angle s should be in theorder of to 31. with this construction, slightly different effects areobtained by varying the depth of immersion of the area relative to thesurface of the water, although it is to be understood that in no case isthe aerator run completely beneath the surface of the water.

FIG. 15 shows a modified form of the invention wherein the aerator arms22d are formed so that their upper and lower plates 36d, 38d convergeslightly towards their trailing edges. The vanes 40d extend generallyvertically between the plates 36d, 38d in the manner previouslydescribed and in accordance with FIGS. 8 11.

This relative inclination of the cover plates for the blades provides aslight additional acceleration of the jet streams S withoutsubstantially increasing the horsepower requirements of the aerator.

FIG. 16 is a diagrammatic view illustrating the formation of the jetstreams S as they emerge from the trailing ends of the jet formers 22.Air bubbles are shown at A to indicate schematically the entrainment ofair by the jet streams, with resultant oxygenization of the surroundingliquid during operation of the aerator.

FIG. 17 is a plan view of a tank T embodying an aerator of the presentinvention and it shows how the jet stream S although they graduallydiverge and may take curved paths, remain intact as moving bodies ofwater in the tank liquid until they reach the mouth of the tank. Whenthese jet streams S reach the walls of the tank, they are graduallydeflected downwardly and eventually work their way back into the aeratorvia the v whirlpool W as previously described in connection with FIG. 3.In the meantime, the oxygen in the air bubbles entrained by the jetstreams is gradually dissolved by the water over a substantial portionof the tank volume.

RE'SUME'OF THE INVENTION Having described several forms of an improved,low power, high efficiency aerator, a resume of the features andadvantages of the aerator will be presented briefly by way of summaryThe aerator of the present invention requires no baffles to abruptlyproduce a turbulent change in direction of the water entering jetformers, the deposit of material in the jet passages, such as bits ofpaper or the like, does not occur with the resultant clogging of thepassages.

An important requirement in mechanical aerators is that of prolongingthe circulation of water that has entrained air, in order to provideoxygenization of as much as possible of the body of liquid in the tank.The aerators of the present invention produce oxygen laden jet streamsthat are long lasting, homogenous and have a relatively high horizontalsurface velocity. This enables the jet streams to maintain theirindividuality and air entrainment action all the way to the wall of areasonably sized tank. Furthermore, the jet streams are deflected at thetank wall and move down into the body of liquid. As a result of this,the entrained air incorporated into the jet streams providesoxygenization of the tank water over a large portion of its volume.

In a preferred embodiment of the invention, the top plates that coverthe aerator vanes are wider than the bottom plates, so that the jets aremaintained in the horizontal plane thereby reducing the amount of watersprayed into the atmosphere with an accompanying loss of effectivenessand increase in power requirements.

A feature of the present invention is that with modest powerrequirements, the aerator produces high velocity, smooth flowing, longlasting jet streams. These streams are generated by the inclination ofthe vanes relative to the tangent to their paths of motion through thewater. Also, although the vanes may be straight (FIGS. 1 4) it has beenfound that curved vanes (FIG. 8) provide better acceleration of thewater and thus facilitate the formation of the type of effective jetstreams characteristic of the present invention.

It has been found that the aerator of the present invention, although itoperates at the surface level of water in the tank, does not ice up andhence does not provide power and clogging problems as the result of icefound under difiicult climactic conditions.

A feature of the present invention is that the amount of aeration for agiven power input, or the amount of power input itself can be preciselycontrolled by simply varying the degree to which vertical vanes of thejet formers are submerged in the surface layer of water.-

the proper size of hub or float on which the arms are mounted and byselecting an appropriate number of arms.

The jet formers of the present invention can be characterized as largediameter, short length tubes, (preferably square tubes) which are movedat a relatively small inclination through the water and thus produceeffective jet streams with low horsepower requirements without cloggingproblems. These tubes themselves are of such simple construction thatthey can be fabricated by conventional sheet metal operations whicheconomies are implemented by the fact that the arms can be of modularconstruction, forming the basis for a number of aerators of variousspecifications.

Although the aerators of the present invention are effective inproducing long lasting horizontal jet streams that are diverted at thetank walls, these streams are produced in a relatively nonturbulentfashion which do not upset the normal flow pattern of the water.

The aerator of the present invention can be readily provided with acentral float forming the hub of the aerator, or with such a floataugmented by attachment of cone for centering the whirlpool relative tothe aerator.

Although the best mode contemplated for carrying out the presentinvention has been herein shown and described it will be apparent thatmodification and variation may be made without departing from what isregarded to be the subject matter of the invention.

lclaim:

1. A mechanical aerator for introducing oxygen into a body of liquidcomprising a generally vertical shaft, means for rotating said shaft,means mounting a plurality of circumferentially spaced, box-like jetformers on said shaft for rotation at the surface layer of liquid withthe inlets and outlets of said jet formers partially submerged in theliquid; said jet formers comprising upstanding radially spaced vanesthat are generally parallel, upper and lower closure plates for thevanes, said lower closure plates being circumferentially spaced toprovide for the entry of liquid from below, the circumferential extentof said vanes being not substantially greater than twice the radialspacing of adjacent vanes, said vanes having their leading edges on asmaller radius of rotation than their trailing edges for horizontallyaccelerating the surface layer of liquid into diverging jet streams.

2. The aerator of claim 1, wherein said jet former closure plates areradially continuous with at least three substantially equally spacedvanes extending between the plates.

3. The aerator of claim 2, wherein the upper closure plates overhang theleading and trailing edges of said vanes.

4. The aerator of claim 3, wherein thelower closure plates aresubstantially horizontally coextensive with said vanes.

5. The aerator of claim 2, wherein said closure plates converge slightlytoward their trailing edges.

6. The aerator of claim 2, wherein said vanes are curved with theirconcave faces facing forwardly.

7. The aerator of claim 6, wherein the leading portions of said vanesare straight.

8. The aerator of claim 1, wherein the circumferential extent of saidvanes is in the range of about one half to one times the radial spacingof the vanes.

9. The aerator of claim 1, wherein the height of said vanes is in therange of about one to 1 times the radial spacing of the vanes.

10. The aerator of claim 8, wherein the height of said vanes is in therange of about one to l V; times the radial spacing of the vanes.

11. The aerator of claim 1, wherein the velocity of said vanes is about10 2O feet/second. v

12. The aerator of claim 1, wherein said jet formers are disposed sothat the upper ends of said vanes are above the surface of the tankliquid.

13. An aerator for introducing oxygen into liquid in a tank comprising agenerally vertical shaft, means for rotating said shaft, upper and lowerhub discs on said shaft at the surface layer of liquid in the tank, aplurality of pairs of vertically spaced, spoke-like plates projectingradially from said discs, a plurality of liquid accelerating vanesextending generally vertically between each pair of plates to providearms embodying box-like jet formers, said vanes having their leadingedges on a smaller radius of rotation than their trailing edges forhorizontally accelerating the surface layer of liquid into diverging jetstreams.

14. The aerator of claim 13, wherein said hub discs are peripherallyconnected by a cylindrical baffle.

15. The aerator of claim 14, wherein said hub is watertight to form afloat.

16. The aerator of claim 13, comprising a cone projecting down from thelower hub disc for controlling the whirlpool below the aerator.

17. The aerator of claim 13, wherein said jet former arms are inclinedupwardly from their radially inner ends at about 10 to 30.

18. A mechanical aerator for a large body of liquid comprising avertical shaft, a plurality of relatively short, large cross sectioncircumferentially extending jet forming tubes mounted on said shaft andat a substantial radial distance therefrom, said jet forming inclinedabout 10 to 30'with said tangent to their paths of rotation.

20. The aerator of claim 1, wherein said upper and lower closure platesare substantially flat and parallel and with the upper closure platebeing disposed above the liquid surface.

1. A mechanical aerator for introducing oxygen into a body of liquidcomprising a generally vertical shaft, means for rotating said shaft,means mounting a plurality of circumferentially spaced, box-like jetformers on said shaft for rotation at the surface layer of liquid withthe inlets and outlets of said jet formers partially submerged in theliquid; said jet formers comprising upstanding radially spaced vanesthat are generally parallel, upper and lower closure plates for thevanes, said lower closure plates being circumferentially spaced toprovide for the entry of liquid from below, the circumferential extentof said vanes being not substantially greater than twice the radialspacing of adjacent vanes, said vanes having their leading edges on asmaller radius of rotation than their trailing edges for horizontallyaccelerating the surface layer of liquid into diverging jet streams. 2.The aerator of claim 1, wherein said jet former closure plates areradially continuous with at least three substantially equally spacedvanes extending between the plates.
 3. The aerator of claim 2, whereinthe upper closure plates overhang the leading and trailing edges of saidvanes.
 4. The aerator of claim 3, wherein the lower closure plates aresubstantially horizontally coextensive with said vanes.
 5. The aeratorof claim 2, wherein said closure plates converge slightly toward theirtrailing edges.
 6. The aerator of claim 2, wherein said vanes are curvedwith their concave faces facing forwardly.
 7. The aerator of claim 6,wherein the leading portions of said vanes are straight.
 8. The aeratorof claim 1, wherein the circumferential extent of said vanes is in therange of about one half to one times the radial spacing of the vanes. 9.The aerator of claim 1, wherein the height of said vanes is in the rangeof about one to 1 1/2 times the radial spacing of the vanes.
 10. Theaerator of claim 8, wherein the height of said vanes is in the range ofabout one to 1 1/2 times the radial spacing of the vanes.
 11. Theaerator of claim 1, wherein the velocity of said vanes is about 10 - 20feet/second.
 12. The aerator of claim 1, wherein said jet formers aredisposed so that the upper ends of said vanes are above the surface ofthe tank liquid.
 13. An aerator for introducing oxygen into liquid in atank comprising a generally vertical shaft, means for rotating saidshaft, upper and lower hub discs on said shaft at the surface layer ofliquid in the tank, a plurality of pairs of vertically spaced,spoke-like plates projecting radially from said discs, a plurality ofliquid accelerating vanes extending generally vertically between eachpair of plates to provide arms embodying box-like jet formers, saidvanes having their leading edges on a smaller radius of rotation thantheir trailing edges for horizontally accelerating the surface layer ofliquid into diverging jet streams.
 14. The aerator of claim 13, whereinsaid hub discs are peripherally connected by a cylindrical baffle. 15.The aerator of claim 14, wherein said hub is watertight to form a float.16. The aerator of claim 13, comprising a cone projecting down from thelower hub disc for controlling the whirlpool below the aerator.
 17. Theaerator of claim 13, wherein said jet former arms are inclined upwardlyfrom their radially inner ends at about 10* to 30* .
 18. A mechanicalaerator for a large body of liquid comprising a vertical shaft, aplurality of relatively short, large cross section circumferentiallyextending jet forming tubes mounted on said shaft and at a substantialradial distance therefrom, said jet forming tubes having their sidewallsinclined from a tangent to their path of rotation so that their leadingedges are closer to the shaft than their trailing edges, said tubeshaving a length that is not substantially more than twice theircross-sectional width, and means for rotating said shaft with the tubesat the surface layer of said body of liquid.
 19. The aerator of claim18, wherein said tubes are inclined about 10* to 30* with said tangentto their paths of rotation.
 20. The aerator of claim 1, wherein saidupper and lower closure plates are substantially flat and parallel andwith the upper closure plate being disposed above the liquid surface.